The menu works best with textless menu, the firmware included should be textless, but with the image pack you will have to edit yourself.

Being that the background is black some menu items will be hard to read until you select them, and the Settings > Info screen the text is unreadable.

I did not put the fonts on the image pack because I was having trouble if I edited them, in the firmware so as long as you don't edit the fonts you should be fine.

The black on the Locked box is transparent when viewed on the player.

When Recording Voice or FM the buttons (Pause & Record) can be hard to see, and It's a dark theme overall so in the sunlight it can be hard to see (When you highlight whatever you are looking at it shows up very well though).